perf: 系统级性能优化与并发安全修复

## 并发安全修复 (4处)
- scrap.py: 报废执行添加 SELECT FOR UPDATE 悲观锁，消除 TOCTOU 竞态
- stock.py (adjust_stock): 盘点调整添加 for_update=True 行锁
- outbound_service.py: 低库存预警 SMTP 调用移到 commit 之后，避免长事务
- trans_service.py: execute_dispatch 按 (source_table, id) 排序 items，消除死锁风险

## N+1 查询优化 (2处)
- inventory_task.py: _prefetch_inventory_map 单条 UNION ALL+GROUP BY 替代循环内逐条查询（N*4次→2次）
- stock.py (export_stocktake): get_borrowed_qty 批量 GROUP BY 替代逐条 TransBorrow 查询（~18000次→1次）

## BOM 列表性能重构
- bom_service.py: get_bom_list 单条 GROUP BY+string_agg+分页，消除 N+1 循环查询
- bom_service.py: 新增 get_bom_summary (轻量 GROUP BY category+COUNT)
- bom.py: 新增 /api/v1/bom/summary 路由，/list 支持 category 过滤

## Odoo 基础信息懒加载
- base_service.py: 新增 get_odoo_summary (GROUP BY category+COUNT)
- base.py: 新增 /api/v1/inbound/base/odoo-summary 路由
- buyOdoo.vue: 懒加载分组架构 (fetchOdooSummary + loadGroupItems)
- material_base.ts: 新增 getOdooSummary API

## 前端 Bug 修复
- BomManage.vue: 懒加载分组 (fetchBomSummary + loadGroupItems + collapse)
- BomManage.vue: 适配新 API 格式 (res.data.items 替代 res.data)
- buyOdoo.vue: 移除 "点击展开加载" 文字
- Selection.vue + borrow/apply/index.vue: openBomSelect 适配新 API 格式

inventory-backend/app/services/inventory_task.py

@@ -23,20 +23,65 @@ from app.models.inbound.product import StockProduct
 class InventoryWarningService:
 
     @staticmethod
-    def _get_total_inventory(base_id: int) -> float:
+    def _prefetch_inventory_map(settings):
         """
-        计算指定物料在所有库存表（采购件 + 半成品 + 成品）中的总库存量
+        批量预取所有预警物料的库存总计（单条 SQL，跨三表聚合）
+
+        性能优化（v2）：
+        - 消除 N+1：用 UNION ALL + GROUP BY 替代循环内逐条 scalar 查询
+        - 消除额外的 MaterialBase.get()：批量返回 name / spec_model
+
+        Returns:
+            dict[int, dict]: {base_id: {'inv': float, 'avail': float, 'name': str, 'spec': str}, ...}
         """
-        buy_q = db.session.query(func.sum(StockBuy.stock_quantity)).filter(
-            StockBuy.base_id == base_id
-        ).scalar() or 0
-        semi_q = db.session.query(func.sum(StockSemi.stock_quantity)).filter(
-            StockSemi.base_id == base_id
-        ).scalar() or 0
-        prod_q = db.session.query(func.sum(StockProduct.stock_quantity)).filter(
-            StockProduct.base_id == base_id
-        ).scalar() or 0
-        return float(buy_q) + float(semi_q) + float(prod_q)
+        from sqlalchemy import text
+
+        base_ids = list({s.base_id for s in settings})
+
+        if not base_ids:
+            return {}
+
+        # ── 单条 SQL：三表 UNION ALL → 外层 GROUP BY ──
+        sql = text("""
+            SELECT base_id,
+                   SUM(stock_qty)   AS total_stock,
+                   SUM(avail_qty)   AS total_avail
+            FROM (
+                SELECT base_id, stock_quantity AS stock_qty, available_quantity AS avail_qty
+                FROM stock_buy
+                WHERE base_id = ANY(:ids)
+
+                UNION ALL
+
+                SELECT base_id, stock_quantity, available_quantity
+                FROM stock_semi
+                WHERE base_id = ANY(:ids)
+
+                UNION ALL
+
+                SELECT base_id, stock_quantity, available_quantity
+                FROM stock_product
+                WHERE base_id = ANY(:ids)
+            ) AS combined
+            GROUP BY base_id
+        """)
+        rows = db.session.execute(sql, {'ids': base_ids}).fetchall()
+
+        # 批量查询 MaterialBase
+        materials = MaterialBase.query.filter(MaterialBase.id.in_(base_ids)).all()
+        mat_map = {m.id: {'name': m.name, 'spec': m.spec_model or ''} for m in materials}
+
+        result = {}
+        for row in rows:
+            bid = row.base_id
+            mat = mat_map.get(bid, {'name': '', 'spec': ''})
+            result[bid] = {
+                'inv': float(row.total_stock or 0),
+                'avail': float(row.total_avail or 0),
+                'name': mat['name'],
+                'spec': mat['spec']
+            }
+        return result
 
     @staticmethod
     def _parse_emails(email_str: str) -> list:
@@ -106,17 +151,20 @@ class InventoryWarningService:
         sent_yellow = False
         processed_settings = []
 
+        # ★ 性能优化：批量预取所有 setting 对应的库存 + 物料信息（1 条 SQL 替代 N*4 条）
+        inv_map = InventoryWarningService._prefetch_inventory_map(settings)
+
         for setting in settings:
             base_id = setting.base_id
-            material = MaterialBase.query.get(base_id)
-            if not material:
+            mat_data = inv_map.get(base_id)
+            if not mat_data:
                 continue
 
-            name = material.name
-            spec = material.spec_model or ''
+            name = mat_data['name']
+            spec = mat_data['spec']
+            inv = mat_data['inv']
             red_th = float(setting.red_threshold) if setting.red_threshold is not None else None
             yellow_th = float(setting.yellow_threshold) if setting.yellow_threshold is not None else None
-            inv = InventoryWarningService._get_total_inventory(base_id)
 
             # ★ 红色预警：库存 <= red_threshold，走 setting.red_emails ★
             if red_th is not None and inv <= red_th: